Bump version to 0.5.2

readme.md

@@ -6,7 +6,7 @@ Markdig is a fast, powerfull, [CommonMark](http://commonmark.org/) compliant, ex
 
 > NOTE: The repository is under construction. There will be a dedicated website and proper documentation at some point!
 
-You can **try Markdig online** and compare it to other implementations on [babelmark3](http://babelmark.github.io/) 
+You can **try Markdig online** and compare it to other implementations on [babelmark3](https://babelmark.github.io/?text=Hello+**Markdig**!)
 
 ## Features
 
@@ -18,7 +18,7 @@ You can **try Markdig online** and compare it to other implementations on [babel
   - including GFM fenced code blocks. 
 - **Extensible** architecture
   - Even the core Markdown/CommonMark parsing is pluggable, so it allows to disable builtin Markdown/Commonmark parsing (e.g [Disable HTML parsing](https://github.com/lunet-io/markdig/blob/7964bd0160d4c18e4155127a4c863d61ebd8944a/src/Markdig/MarkdownExtensions.cs#L306)) or change behaviour (e.g change matching `#` of a headers with `@`)   
-- Built-in with **18+ extensions**, including:
+- Built-in with **20+ extensions**, including:
   - 2 kind of tables:
     - **Pipe tables** (inspired from Github tables and [PanDoc - Pipe Tables](http://pandoc.org/README.html#extension-pipe_tables))
     - **Grid tables** (inspired from [Pandoc - Grid Tables](http://pandoc.org/README.html#extension-grid_tables)) 
@@ -32,6 +32,7 @@ You can **try Markdig online** and compare it to other implementations on [babel
   - **Definition lists** (inspired from [PHP Markdown Extra - Definitions Lists](https://michelf.ca/projects/php-markdown/extra/#def-list))
   - **Footnotes** (inspired from [PHP Markdown Extra - Footnotes](https://michelf.ca/projects/php-markdown/extra/#footnotes))
   - **Auto-identifiers** for headings (similar to [Pandoc - Auto Identifiers](http://pandoc.org/README.html#extension-auto_identifiers))
+  - **Task Lists** inspired from [Github Task lists](https://github.com/blog/1375-task-lists-in-gfm-issues-pulls-comments).
   - **Extra bullet lists**, supporting alpha bullet `a.` `b.` and roman bullet (`i`, `ii`...etc.)
   - **Media support** for media url (youtube, vimeo, mp4...etc.) (inspired from this [CommonMark discussion](https://talk.commonmark.org/t/embedded-audio-and-video/441))
   - **Abbreviations** (inspired from [PHP Markdown Extra - Abbreviations](https://michelf.ca/projects/php-markdown/extra/#abbr))
@@ -46,6 +47,13 @@ You can **try Markdig online** and compare it to other implementations on [babel
   - **Bootstrap** class (to output bootstrap class)
 - Compatible with .NET 3.5, 4.0+ and .NET Core (`netstandard1.1+`)
 	
+## Documentation
+
+> The repository is under construction. There will be a dedicated website and proper documentation at some point!
+
+In the meantime, you can have a "behind the scene" article about Markdig in my blog post ["Implementing a Markdown Engine for .NET"](http://xoofx.com/blog/2016/06/13/implementing-a-markdown-processor-for-dotnet/)
+
+
 ## Download
 
 Markdig is available as a NuGet package: [![NuGet](https://img.shields.io/nuget/v/Markdig.svg)](https://www.nuget.org/packages/Markdig/)
@@ -80,27 +88,44 @@ This software is released under the [BSD-Clause 2 license](https://github.com/lu
 
 This is an early preview of the benchmarking against various implementations:
 
-- Markdig: itself
-- CommonMarkCpp: [cmark](https://github.com/jgm/cmark), Reference C implementation of CommonMark, no support for extensions
-- [CommonMark.NET](https://github.com/Knagis/CommonMark.NET): CommonMark implementation for .NET, no support for extensions, port of cmark
-  - [CommonMarkNet (devel)](https://github.com/AMDL/CommonMark.NET/tree/pipe-tables): An evolution of CommonMark.NET, supports extensions, not released yet
-- [MarkdownDeep](https://github.com/toptensoftware/markdowndeep) another .NET implementation
-- [MarkdownSharp](https://github.com/Kiri-rin/markdownsharp): Open source C# implementation of Markdown processor, as featured on Stack Overflow, regexp based.
-- [Moonshine](https://github.com/brandonc/moonshine): popular C Markdown processor
+**C implementations**:
+
+- [cmark](https://github.com/jgm/cmark) (version: 0.25.0): Reference C implementation of CommonMark, no support for extensions
+- [Moonshine](https://github.com/brandonc/moonshine) (version: : popular C Markdown processor
+
+**.NET implementations**:
+
+- [Markdig](https://github.com/lunet-io/markdig) (version: 0.5.x): itself
+- [CommonMark.NET(master)](https://github.com/Knagis/CommonMark.NET) (version: 0.11.0): CommonMark implementation for .NET, no support for extensions, port of cmark
+  - [CommonMark.NET(pipe_tables)](https://github.com/AMDL/CommonMark.NET/tree/pipe-tables): An evolution of CommonMark.NET, supports extensions, not released yet
+- [MarkdownDeep](https://github.com/toptensoftware/markdowndeep) (version: 1.5.0): another .NET implementation
+- [MarkdownSharp](https://github.com/Kiri-rin/markdownsharp) (version: 1.13.0): Open source C# implementation of Markdown processor, as featured on Stack Overflow, regexp based.
+- [Marked.NET](https://github.com/T-Alex/MarkedNet) (version: 1.0.5) port of original [marked.js](https://github.com/chjj/marked) project
+- [Microsoft.DocAsCode.MarkdownLite](https://github.com/dotnet/docfx/tree/dev/src/Microsoft.DocAsCode.MarkdownLite) (version: 2.0.1) used by the [docfx](https://github.com/dotnet/docfx) project
+
+**JavaScript/V8 implementations**:
+
+- [Strike.V8](https://github.com/SimonCropp/Strike) (version: 1.5.0)  [marked.js](https://github.com/chjj/marked) running in Google V8 (not .NET based)
 
 ### Analysis of the results:
 
-- Markdig is roughly **x100 times faster than MarkdownSharp**
+- Markdig is roughly **x100 times faster than MarkdownSharp**, **30x times faster than docfx**
 - **Among the best in CPU**, Extremelly competitive and often faster than other implementations (not feature wise equivalent) 
 - **15% to 30% less allocations** and GC pressure
 
+Because Marked.NET,  MarkdownSharp and DocAsCode.MarkdownLite are way too slow, they are not included in the following charts:
 
-### Performance in x86:
+![BenchMark CPU Time](img/BenchmarkCPU.png)
+
+![BenchMark Memory](img/BenchmarkMemory.png)
+
+
+### Performance for x86:
 
 ```
-BenchmarkDotNet-Dev=v0.9.6.0+
+BenchmarkDotNet-Dev=v0.9.7.0+
 OS=Microsoft Windows NT 6.2.9200.0
-Processor=Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz, ProcessorCount=8
+Processor=Intel(R) Core(TM) i7-4770 CPU 3.40GHz, ProcessorCount=8
 Frequency=3319351 ticks, Resolution=301.2637 ns, Timer=TSC
 HostCLR=MS.NET 4.0.30319.42000, Arch=32-bit RELEASE
 JitModules=clrjit-v4.6.1080.0
@@ -108,14 +133,18 @@ JitModules=clrjit-v4.6.1080.0
 Type=Program  Mode=SingleRun  LaunchCount=2
 WarmupCount=2  TargetCount=10
 
-               Method |    Median |    StdDev |  Gen 0 | Gen 1 |  Gen 2 | Bytes Allocated/Op |
---------------------- |---------- |---------- |------- |------ |------- |------------------- |
-          TestMarkdig | 5.4332 ms | 0.0809 ms |  96.00 | 36.00 |  84.00 |       1,218,643.59 |
-    TestCommonMarkCpp | 4.0150 ms | 0.1208 ms |      - |     - | 180.00 |         454,859.74 |
-    TestCommonMarkNet | 4.5448 ms | 0.0323 ms | 193.00 | 12.00 |  84.00 |       1,406,367.27 |
- TestCommonMarkNetNew | 5.4811 ms | 0.0327 ms | 193.00 | 96.00 |  84.00 |       1,738,465.42 |
-     TestMarkdownDeep | 7.5881 ms | 0.0554 ms | 205.00 | 96.00 |  84.00 |       1,758,383.79 |
-        TestMoonshine | 5.8586 ms | 0.0764 ms |      - |     - | 215.00 |         565,000.72 |
+                     Method |      Median |    StdDev |Scaled |  Gen 0 | Gen 1|    Gen 2|Bytes Allocated/Op |
+--------------------------- |------------ |---------- |------ | ------ |------|---------|------------------ |
+                    Markdig |   5.5316 ms | 0.0372 ms |  0.71 |   56.00| 21.00|    49.00|      1,285,917.31 |
+     CommonMark.NET(master) |   4.7035 ms | 0.0422 ms |  0.60 |  113.00|  7.00|    49.00|      1,502,404.60 |
+CommonMark.NET(pipe_tables) |   5.6164 ms | 0.0298 ms |  0.72 |  111.00| 56.00|    49.00|      1,863,128.13 |
+               MarkdownDeep |   7.8193 ms | 0.0334 ms |  1.00 |  120.00| 56.00|    49.00|      1,884,854.85 |
+                      cmark |   4.2698 ms | 0.1526 ms |  0.55 |       -|     -|        -|                NA |
+                  Moonshine |   6.0929 ms | 0.1053 ms |  1.28 |       -|     -|        -|                NA |
+                  Strike.V8 |  10.5895 ms | 0.0492 ms |  1.35 |       -|     -|        -|                NA |
+                 Marked.NET | 207.3169 ms | 5.2628 ms | 26.51 |    0.00|  0.00|     0.00|    303,125,228.65 |
+              MarkdownSharp | 675.0185 ms | 2.8447 ms | 86.32 |   40.00| 27.00|    41.00|      2,413,394.17 |
+Microsoft DocfxMarkdownLite | 166.3357 ms | 0.4529 ms | 21.27 |4,452.00|948.00|11,167.00|    180,218,359.60 |
 ```
 
 ### Performance for x64:

src/Markdig.Tests/Markdig.Tests.csproj

@@ -83,6 +83,7 @@
     <None Include="Specs\GridTableSpecs.md" />
     <None Include="Specs\HardlineBreakSpecs.md" />
     <None Include="Specs\BootstrapSpecs.md" />
+    <None Include="Specs\TaskListSpecs.md" />
     <None Include="Specs\SmartyPantsSpecs.md" />
     <None Include="Specs\MediaSpecs.md" />
     <None Include="Specs\MathSpecs.md" />

src/Markdig.Tests/Specs/Specs.cs

@@ -19190,4 +19190,58 @@ namespace Markdig.Tests
 			TestParser.TestSpec("[With a new text][This is a heading]\n# This is a heading", "<p><a href=\"#this-is-a-heading\">With a new text</a></p>\n<h1 id=\"this-is-a-heading\">This is a heading</h1>", "autoidentifiers");
         }
     }
+        // # Extensions
+        //
+        // Adds support for task lists:
+        //
+        // ## TaskLists
+        //
+        // A task list item consist of `[ ]` or `[x]` or `[X]` inside a list item (ordered or unordered)
+    [TestFixture]
+    public partial class TestExtensionsTaskLists
+    {
+        [Test]
+        public void Example001()
+        {
+            // Example 1
+            // Section: Extensions TaskLists
+            //
+            // The following CommonMark:
+            //     - [ ] Item1
+            //     - [x] Item2
+            //     - [ ] Item3
+            //     - Item4
+            //
+            // Should be rendered as:
+            //     <ul>
+            //     <li><input disabled="disabled" type="checkbox" /> Item1</li>
+            //     <li><input disabled="disabled" type="checkbox" checked="checked" /> Item2</li>
+            //     <li><input disabled="disabled" type="checkbox" /> Item3</li>
+            //     <li>Item4</li>
+            //     </ul>
+
+            Console.WriteLine("Example {0}" + Environment.NewLine + "Section: {0}" + Environment.NewLine, 1, "Extensions TaskLists");
+			TestParser.TestSpec("- [ ] Item1\n- [x] Item2\n- [ ] Item3\n- Item4", "<ul>\n<li><input disabled=\"disabled\" type=\"checkbox\" /> Item1</li>\n<li><input disabled=\"disabled\" type=\"checkbox\" checked=\"checked\" /> Item2</li>\n<li><input disabled=\"disabled\" type=\"checkbox\" /> Item3</li>\n<li>Item4</li>\n</ul>", "tasklists");
+        }
+    }
+        // A task is not recognized outside a list item:
+    [TestFixture]
+    public partial class TestExtensionsTaskLists
+    {
+        [Test]
+        public void Example002()
+        {
+            // Example 2
+            // Section: Extensions TaskLists
+            //
+            // The following CommonMark:
+            //     [ ] This is not a task list
+            //
+            // Should be rendered as:
+            //     <p>[ ] This is not a task list</p>
+
+            Console.WriteLine("Example {0}" + Environment.NewLine + "Section: {0}" + Environment.NewLine, 2, "Extensions TaskLists");
+			TestParser.TestSpec("[ ] This is not a task list", "<p>[ ] This is not a task list</p>", "tasklists");
+        }
+    }
 }

src/Markdig.Tests/Specs/Specs.tt

@@ -56,6 +56,7 @@ SOFTWARE.
 		new KeyValuePair<string, string>(Host.ResolvePath("MediaSpecs.md"), "medialinks"),
 		new KeyValuePair<string, string>(Host.ResolvePath("SmartyPantsSpecs.md"), "smartypants"),
 		new KeyValuePair<string, string>(Host.ResolvePath("AutoIdentifierSpecs.md"), "autoidentifiers"),
+		new KeyValuePair<string, string>(Host.ResolvePath("TaskListSpecs.md"), "tasklists"),
 	};
     var emptyLines = false;
     var displayEmptyLines = false;

src/Markdig.Tests/Specs/TaskListSpecs.md

@@ -0,0 +1,29 @@
+# Extensions
+
+Adds support for task lists:
+
+## TaskLists
+ 
+A task list item consist of `[ ]` or `[x]` or `[X]` inside a list item (ordered or unordered)
+
+```````````````````````````````` example
+- [ ] Item1
+- [x] Item2
+- [ ] Item3
+- Item4
+.
+<ul>
+<li><input disabled="disabled" type="checkbox" /> Item1</li>
+<li><input disabled="disabled" type="checkbox" checked="checked" /> Item2</li>
+<li><input disabled="disabled" type="checkbox" /> Item3</li>
+<li>Item4</li>
+</ul>
+````````````````````````````````
+
+A task is not recognized outside a list item:
+
+```````````````````````````````` example
+[ ] This is not a task list
+.
+<p>[ ] This is not a task list</p>
+````````````````````````````````

src/Markdig.Tests/TestLinkHelper.cs

@@ -80,36 +80,52 @@ namespace Markdig.Tests
         [Test]
         public void TestUrlAndTitle()
         {
+            //                           0         1         2         3
+            //                           0123456789012345678901234567890123456789
             var text = new StringSlice(@"(http://google.com 'this is a title')ABC");
             string link;
             string title;
-            Assert.True(LinkHelper.TryParseInlineLink(ref text, out link, out title));
+            SourceSpan linkSpan;
+            SourceSpan titleSpan;
+            Assert.True(LinkHelper.TryParseInlineLink(ref text, out link, out title, out linkSpan, out titleSpan));
             Assert.AreEqual("http://google.com", link);
             Assert.AreEqual("this is a title", title);
+            Assert.AreEqual(new SourceSpan(1, 17), linkSpan);
+            Assert.AreEqual(new SourceSpan(19, 35), titleSpan);
             Assert.AreEqual('A', text.CurrentChar);
         }
 
         [Test]
         public void TestUrlAndTitleEmpty()
         {
+            //                           01234
             var text = new StringSlice(@"(<>)A");
             string link;
             string title;
-            Assert.True(LinkHelper.TryParseInlineLink(ref text, out link, out title));
+            SourceSpan linkSpan;
+            SourceSpan titleSpan;
+            Assert.True(LinkHelper.TryParseInlineLink(ref text, out link, out title, out linkSpan, out titleSpan));
             Assert.AreEqual(string.Empty, link);
             Assert.AreEqual(string.Empty, title);
+            Assert.AreEqual(new SourceSpan(1, 2), linkSpan);
+            Assert.AreEqual(SourceSpan.Empty, titleSpan);
             Assert.AreEqual('A', text.CurrentChar);
         }
 
         [Test]
         public void TestUrlAndTitleEmpty2()
         {
+            //                           012345
             var text = new StringSlice(@"( <> )A");
             string link;
             string title;
-            Assert.True(LinkHelper.TryParseInlineLink(ref text, out link, out title));
+            SourceSpan linkSpan;
+            SourceSpan titleSpan;
+            Assert.True(LinkHelper.TryParseInlineLink(ref text, out link, out title, out linkSpan, out titleSpan));
             Assert.AreEqual(string.Empty, link);
             Assert.AreEqual(string.Empty, title);
+            Assert.AreEqual(new SourceSpan(2, 3), linkSpan);
+            Assert.AreEqual(SourceSpan.Empty, titleSpan);
             Assert.AreEqual('A', text.CurrentChar);
         }
 
@@ -117,12 +133,18 @@ namespace Markdig.Tests
         [Test]
         public void TestUrlEmptyWithTitleWithMultipleSpaces()
         {
+            //                           0         1         2
+            //                           0123456789012345678901234567
             var text = new StringSlice(@"(   <>      'toto'       )A");
             string link;
             string title;
-            Assert.True(LinkHelper.TryParseInlineLink(ref text, out link, out title));
+            SourceSpan linkSpan;
+            SourceSpan titleSpan;
+            Assert.True(LinkHelper.TryParseInlineLink(ref text, out link, out title, out linkSpan, out titleSpan));
             Assert.AreEqual(string.Empty, link);
             Assert.AreEqual("toto", title);
+            Assert.AreEqual(new SourceSpan(4, 5), linkSpan);
+            Assert.AreEqual(new SourceSpan(12, 17), titleSpan);
             Assert.AreEqual('A', text.CurrentChar);
         }
 
@@ -132,50 +154,67 @@ namespace Markdig.Tests
             var text = new StringSlice(@"()A");
             string link;
             string title;
-            Assert.True(LinkHelper.TryParseInlineLink(ref text, out link, out title));
+            SourceSpan linkSpan;
+            SourceSpan titleSpan;
+            Assert.True(LinkHelper.TryParseInlineLink(ref text, out link, out title, out linkSpan, out titleSpan));
             Assert.AreEqual(string.Empty, link);
             Assert.AreEqual(string.Empty, title);
+            Assert.AreEqual(SourceSpan.Empty, linkSpan);
+            Assert.AreEqual(SourceSpan.Empty, titleSpan);
             Assert.AreEqual('A', text.CurrentChar);
         }
 
         [Test]
         public void TestMultipleLines()
         {
-            var text = new StringSlice(@"(
-                   <http://google.com>  
-                 'toto' )A");
+            //                          0          1         2          3
+            //                          01 2345678901234567890 1234567890123456789
+            var text = new StringSlice("(\n<http://google.com>\n    'toto' )A");
             string link;
             string title;
-            Assert.True(LinkHelper.TryParseInlineLink(ref text, out link, out title));
+            SourceSpan linkSpan;
+            SourceSpan titleSpan;
+            Assert.True(LinkHelper.TryParseInlineLink(ref text, out link, out title, out linkSpan, out titleSpan));
             Assert.AreEqual("http://google.com", link);
             Assert.AreEqual("toto", title);
+            Assert.AreEqual(new SourceSpan(2, 20), linkSpan);
+            Assert.AreEqual(new SourceSpan(26, 31), titleSpan);
             Assert.AreEqual('A', text.CurrentChar);
         }
 
         [Test]
         public void TestLabelSimple()
         {
+            //                          01234
             var text = new StringSlice("[foo]");
             string label;
-            Assert.True(LinkHelper.TryParseLabel(ref text, out label));
+            SourceSpan labelSpan;
+            Assert.True(LinkHelper.TryParseLabel(ref text, out label, out labelSpan));
+            Assert.AreEqual(new SourceSpan(1, 3), labelSpan);
             Assert.AreEqual("foo", label);
         }
 
         [Test]
         public void TestLabelEscape()
         {
+            //                           012345678
             var text = new StringSlice(@"[fo\[\]o]");
             string label;
-            Assert.True(LinkHelper.TryParseLabel(ref text, out label));
+            SourceSpan labelSpan;
+            Assert.True(LinkHelper.TryParseLabel(ref text, out label, out labelSpan));
+            Assert.AreEqual(new SourceSpan(1, 7), labelSpan);
             Assert.AreEqual(@"fo[]o", label);
         }
 
         [Test]
         public void TestLabelEscape2()
         {
+            //                           0123
             var text = new StringSlice(@"[\]]");
             string label;
-            Assert.True(LinkHelper.TryParseLabel(ref text, out label));
+            SourceSpan labelSpan;
+            Assert.True(LinkHelper.TryParseLabel(ref text, out label, out labelSpan));
+            Assert.AreEqual(new SourceSpan(1, 2), labelSpan);
             Assert.AreEqual(@"]", label);
         }
 
@@ -194,23 +233,36 @@ namespace Markdig.Tests
         [Test]
         public void TestLabelWhitespaceCollapsedAndTrim()
         {
+            //                           0         1         2         3
+            //                           0123456789012345678901234567890123456789
             var text = new StringSlice(@"[     fo    o    z     ]");
             string label;
-            Assert.True(LinkHelper.TryParseLabel(ref text, out label));
+            SourceSpan labelSpan;
+            Assert.True(LinkHelper.TryParseLabel(ref text, out label, out labelSpan));
+            Assert.AreEqual(new SourceSpan(6, 17), labelSpan);
             Assert.AreEqual(@"fo o z", label);
         }
 
         [Test]
         public void TestlLinkReferenceDefinitionSimple()
         {
+            //                           0         1         2         3
+            //                           0123456789012345678901234567890123456789
             var text = new StringSlice(@"[foo]: /toto 'title'");
             string label;
             string url;
             string title;
-            Assert.True(LinkHelper.TryParseLinkReferenceDefinition(ref text, out label, out url, out title));
+            SourceSpan labelSpan;
+            SourceSpan urlSpan;
+            SourceSpan titleSpan;
+            Assert.True(LinkHelper.TryParseLinkReferenceDefinition(ref text, out label, out url, out title, out labelSpan, out urlSpan, out titleSpan));
             Assert.AreEqual(@"foo", label);
             Assert.AreEqual(@"/toto", url);
             Assert.AreEqual(@"title", title);
+            Assert.AreEqual(new SourceSpan(1, 3), labelSpan);
+            Assert.AreEqual(new SourceSpan(7, 11), urlSpan);
+            Assert.AreEqual(new SourceSpan(13, 19), titleSpan);
+
         }
 
         [Test]

src/Markdig.Tests/TestSourcePosition.cs

@@ -3,10 +3,13 @@
 // See the license.txt file in the project root for more information.
 
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using System.Text;
 using Markdig.Helpers;
 using Markdig.Renderers.Html;
 using Markdig.Syntax;
+using Markdig.Syntax.Inlines;
 using NUnit.Framework;
 
 namespace Markdig.Tests
@@ -162,6 +165,47 @@ literal      ( 0, 4)  4-5
 ");
         }
 
+        [Test]
+        public void TestLinkParts1()
+        {
+            //                         0           1
+            //                         01 2 3456789012345
+            var link = Markdown.Parse("0\n\n01 [234](/56)", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<LinkInline>().FirstOrDefault();
+            Assert.NotNull(link);
+
+            Assert.AreEqual(new SourceSpan(7, 9), link.LabelSpan);
+            Assert.AreEqual(new SourceSpan(12, 14), link.UrlSpan);
+            Assert.AreEqual(SourceSpan.Empty, link.TitleSpan);
+        }
+
+        [Test]
+        public void TestLinkParts2()
+        {
+            //                         0           1
+            //                         01 2 34567890123456789
+            var link = Markdown.Parse("0\n\n01 [234](/56 'yo')", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<LinkInline>().FirstOrDefault();
+            Assert.NotNull(link);
+
+            Assert.AreEqual(new SourceSpan(7, 9), link.LabelSpan);
+            Assert.AreEqual(new SourceSpan(12, 14), link.UrlSpan);
+            Assert.AreEqual(new SourceSpan(16, 19), link.TitleSpan);
+        }
+
+
+        [Test]
+        public void TestLinkParts3()
+        {
+            //                         0           1
+            //                         01 2 3456789012345
+            var link = Markdown.Parse("0\n\n01![234](/56)", new MarkdownPipelineBuilder().UsePreciseSourceLocation().Build()).Descendants().OfType<LinkInline>().FirstOrDefault();
+            Assert.NotNull(link);
+
+            Assert.AreEqual(new SourceSpan(5, 15), link.Span);
+            Assert.AreEqual(new SourceSpan(7, 9), link.LabelSpan);
+            Assert.AreEqual(new SourceSpan(12, 14), link.UrlSpan);
+            Assert.AreEqual(SourceSpan.Empty, link.TitleSpan);
+        }
+
         [Test]
         public void TestHtmlInline()
         {
@@ -479,7 +523,7 @@ literal      ( 0, 0)  0-0
 linebreak    ( 0, 1)  1-1
 literal      ( 1, 0)  2-5
 math         ( 1, 4)  6-11
-attributes   ( 0, 0)  0-0
+attributes   ( 0, 0)  0--1
 ", "mathematics");
         }
 
@@ -562,6 +606,54 @@ literal      ( 4, 2) 13-13
 ", "pipetables");
         }
 
+        [Test]
+        public void TestIndentedCode()
+        {
+            //     01 2 345678 9ABCDE
+            Check("0\n\n    0\n    1\n", @"
+paragraph    ( 0, 0)  0-0
+literal      ( 0, 0)  0-0
+code         ( 2, 4)  7-13
+");
+        }
+
+        [Test]
+        public void TestIndentedCodeWithTabs()
+        {
+            //     01 2 3 45 6 78
+            Check("0\n\n\t0\n\t1\n", @"
+paragraph    ( 0, 0)  0-0
+literal      ( 0, 0)  0-0
+code         ( 2, 4)  4-7
+");
+        }
+
+        [Test]
+        public void TestIndentedCodeWithMixedTabs()
+        {
+            //     01 2 34 56 78 9
+            Check("0\n\n \t0\n \t1\n", @"
+paragraph    ( 0, 0)  0-0
+literal      ( 0, 0)  0-0
+code         ( 2, 4)  5-9
+");
+        }
+
+        [Test]
+        public void TestTabsInList()
+        {
+            //     012 34 567 89
+            Check("- \t0\n- \t1\n", @"
+list         ( 0, 0)  0-8
+listitem     ( 0, 0)  0-3
+paragraph    ( 0, 4)  3-3
+literal      ( 0, 4)  3-3
+listitem     ( 1, 0)  5-8
+paragraph    ( 1, 4)  8-8
+literal      ( 1, 4)  8-8
+");
+        }
+
         [Test]
         public void TestDocument()
         {
@@ -606,11 +698,11 @@ literal      ( 8, 2) 77-92
             foreach (var val in document.Descendants())
             {
                 var name = GetTypeName(val.GetType());
-                build.Append($"{name,-12} ({val.Line,2},{val.Column,2}) {val.SourceStartPosition,2}-{val.SourceEndPosition}\n");
+                build.Append($"{name,-12} ({val.Line,2},{val.Column,2}) {val.Span.Start,2}-{val.Span.End}\n");
                 var attributes = val.TryGetAttributes();
                 if (attributes != null)
                 {
-                    build.Append($"{"attributes",-12} ({attributes.Line,2},{attributes.Column,2}) {attributes.SourceStartPosition,2}-{attributes.SourceEndPosition}\n");
+                    build.Append($"{"attributes",-12} ({attributes.Line,2},{attributes.Column,2}) {attributes.Span.Start,2}-{attributes.Span.End}\n");
                 }
             }
             var result = build.ToString().Trim();

src/Markdig/Extensions/Abbreviations/Abbreviation.cs

@@ -33,5 +33,10 @@ namespace Markdig.Extensions.Abbreviations
         /// The text associated to this label.
         /// </summary>
         public StringSlice Text;
+
+        /// <summary>
+        /// The label span
+        /// </summary>
+        public SourceSpan LabelSpan;
     }
 }

src/Markdig/Extensions/Abbreviations/AbbreviationParser.cs

@@ -4,6 +4,7 @@
 using System.Collections.Generic;
 using Markdig.Helpers;
 using Markdig.Parsers;
+using Markdig.Syntax;
 using Markdig.Syntax.Inlines;
 
 namespace Markdig.Extensions.Abbreviations
@@ -38,8 +39,9 @@ namespace Markdig.Extensions.Abbreviations
                 return BlockState.None;
             }
 
+            SourceSpan labelSpan;
             string label;
-            if (!LinkHelper.TryParseLabel(ref slice, out label))
+            if (!LinkHelper.TryParseLabel(ref slice, out label, out labelSpan))
             {
                 return BlockState.None;
             }
@@ -57,10 +59,10 @@ namespace Markdig.Extensions.Abbreviations
             {
                 Label = label,
                 Text = slice,
-                SourceStartPosition = startPosition,
-                SourceEndPosition = slice.End,
+                Span = new SourceSpan(startPosition, slice.End),
                 Line = processor.LineIndex,
-                Column = processor.Column
+                Column = processor.Column,
+                LabelSpan = labelSpan,
             };
             if (!processor.Document.HasAbbreviations())
             {
@@ -126,8 +128,7 @@ namespace Markdig.Extensions.Abbreviations
                         {
                             container = new ContainerInline()
                             {
-                                SourceStartPosition = originalLiteral.SourceStartPosition,
-                                SourceEndPosition = originalLiteral.SourceEndPosition,
+                                Span = originalLiteral.Span,
                                 Line = originalLiteral.Line,
                                 Column = originalLiteral.Column,
                             };
@@ -137,18 +138,21 @@ namespace Markdig.Extensions.Abbreviations
                         int column;
                         var abbrInline = new AbbreviationInline(abbr)
                         {
-                            SourceStartPosition = processor.GetSourcePosition(i, out line, out column),
+                            Span =
+                            {
+                                Start = processor.GetSourcePosition(i, out line, out column),
+                            },
                             Line = line,
                             Column = column
                         };
-                        abbrInline.SourceEndPosition = abbrInline.SourceStartPosition + match.Length - 1;
+                        abbrInline.Span.End = abbrInline.Span.Start + match.Length - 1;
 
                         // Append the previous literal
                         if (i > content.Start)
                         {
                             container.AppendChild(literal);
 
-                            literal.SourceEndPosition = abbrInline.SourceStartPosition - 1;
+                            literal.Span.End = abbrInline.Span.Start - 1;
                             // Truncate it before the abbreviation
                             literal.Content.End = i - 1;
                         }
@@ -167,8 +171,7 @@ namespace Markdig.Extensions.Abbreviations
                         // Process the remaining literal
                         literal = new LiteralInline()
                         {
-                            SourceStartPosition = abbrInline.SourceEndPosition + 1,
-                            SourceEndPosition = literal.SourceEndPosition,
+                            Span = new SourceSpan(abbrInline.Span.End + 1, literal.Span.End),
                             Line = line,
                             Column = column + match.Length,
                         };

src/Markdig/Extensions/DefinitionLists/DefinitionListParser.cs

@@ -66,8 +66,7 @@ namespace Markdig.Extensions.DefinitionLists
             {
                 currentDefinitionList = new DefinitionList(this)
                 {
-                    SourceStartPosition = paragraphBlock.SourceStartPosition,
-                    SourceEndPosition = processor.Line.End,
+                    Span = new SourceSpan(paragraphBlock.Span.Start, processor.Line.End),
                     Column = paragraphBlock.Column,
                     Line = paragraphBlock.Line,
                 };
@@ -78,8 +77,7 @@ namespace Markdig.Extensions.DefinitionLists
             {
                 Line = processor.LineIndex,
                 Column = column,
-                SourceStartPosition = startPosition,
-                SourceEndPosition = processor.Line.End,
+                Span = new SourceSpan(startPosition, processor.Line.End),
                 OpeningCharacter = processor.CurrentChar,
             };
 
@@ -90,8 +88,7 @@ namespace Markdig.Extensions.DefinitionLists
                 {
                     Column =  paragraphBlock.Column,
                     Line = line.Line,
-                    SourceStartPosition = paragraphBlock.SourceStartPosition,
-                    SourceEndPosition = paragraphBlock.SourceEndPosition,
+                    Span = new SourceSpan(paragraphBlock.Span.Start, paragraphBlock.Span.End),
                     IsOpen = false
                 };
                 term.AppendLine(ref line.Slice, line.Column, line.Line, line.Position);
@@ -101,7 +98,7 @@ namespace Markdig.Extensions.DefinitionLists
             processor.Open(definitionItem);
 
             // Update the end position
-            currentDefinitionList.SourceEndPosition = processor.Line.End;
+            currentDefinitionList.Span.End = processor.Line.End;
 
             return BlockState.Continue;
         }
@@ -136,7 +133,7 @@ namespace Markdig.Extensions.DefinitionLists
                         definitionItem.RemoveAt(definitionItem.Count - 1);
                     }
 
-                    list.SourceEndPosition = list.LastChild.SourceEndPosition;
+                    list.Span.End = list.LastChild.Span.End;
                     return BlockState.None;
                 }
 
@@ -148,8 +145,7 @@ namespace Markdig.Extensions.DefinitionLists
                 processor.Close(definitionItem);
                 var nextDefinitionItem = new DefinitionItem(this)
                 {
-                    SourceStartPosition = startPosition,
-                    SourceEndPosition = processor.Line.End,
+                    Span = new SourceSpan(startPosition, processor.Line.End),
                     Line = processor.LineIndex,
                     Column = processor.Column,
                     OpeningCharacter = processor.CurrentChar,
@@ -182,7 +178,7 @@ namespace Markdig.Extensions.DefinitionLists
                 definitionItem.RemoveAt(definitionItem.Count - 1);
             }
 
-            list.SourceEndPosition = list.LastChild.SourceEndPosition;
+            list.Span.End = list.LastChild.Span.End;
             return BlockState.Break;
         }
     }

src/Markdig/Extensions/Emoji/EmojiParser.cs

@@ -94,12 +94,15 @@ namespace Markdig.Extensions.Emoji
             int column;
             processor.Inline = new EmojiInline(unicode)
             {
-                SourceStartPosition = processor.GetSourcePosition(startPosition, out line, out column),
+                Span =
+                {
+                    Start = processor.GetSourcePosition(startPosition, out line, out column),
+                },
                 Line = line,
                 Column = column,
                 Match = match
             };
-            processor.Inline.SourceEndPosition = processor.Inline.SourceStartPosition + match.Length - 1;
+            processor.Inline.Span.End = processor.Inline.Span.Start + match.Length - 1;
 
             return true;
         }

src/Markdig/Extensions/Figures/FigureBlockParser.cs

@@ -53,8 +53,7 @@ namespace Markdig.Extensions.Figures
 
             var figure = new Figure(this)
             {
-                SourceStartPosition = startPosition,
-                SourceEndPosition = line.End,
+                Span = new SourceSpan(startPosition, line.End),
                 Line = processor.LineIndex,
                 Column = processor.Column,
                 OpeningCharacter = matchChar,
@@ -66,8 +65,7 @@ namespace Markdig.Extensions.Figures
             {
                 var caption = new FigureCaption(this)
                 {
-                    SourceStartPosition = line.Start,
-                    SourceEndPosition = line.End,
+                    Span = new SourceSpan(line.Start, line.End),
                     Line = processor.LineIndex,
                     Column = column + line.Start - startPosition,
                     IsOpen = false
@@ -107,8 +105,7 @@ namespace Markdig.Extensions.Figures
                 {
                     var caption = new FigureCaption(this)
                     {
-                        SourceStartPosition = line.Start,
-                        SourceEndPosition = line.End,
+                        Span = new SourceSpan(line.Start, line.End),
                         Line = processor.LineIndex,
                         Column = column + line.Start - startPosition,
                         IsOpen = false
@@ -117,7 +114,7 @@ namespace Markdig.Extensions.Figures
                     figure.Add(caption);
                 }
 
-                figure.SourceEndPosition = line.End;
+                figure.Span.End = line.End;
 
                 // Don't keep the last line
                 return BlockState.BreakDiscard;
@@ -126,7 +123,7 @@ namespace Markdig.Extensions.Figures
             // Reset the indentation to the column before the indent
             processor.GoToColumn(processor.ColumnBeforeIndent);
 
-            figure.SourceEndPosition = line.End;
+            figure.Span.End = line.End;
 
             return BlockState.Continue;
         }

src/Markdig/Extensions/Footers/FooterBlockParser.cs

@@ -47,8 +47,7 @@ namespace Markdig.Extensions.Footers
             }
             processor.NewBlocks.Push(new FooterBlock(this)
             {
-                SourceStartPosition = startPosition,
-                SourceEndPosition = processor.Line.End,
+                Span = new SourceSpan(startPosition, processor.Line.End),
                 OpeningCharacter = openingChar,
                 Column = column,
                 Line = processor.LineIndex,
@@ -81,7 +80,7 @@ namespace Markdig.Extensions.Footers
                 {
                     processor.NextChar(); // Skip following space
                 }
-                block.SourceEndPosition = processor.Line.End;
+                block.Span.End = processor.Line.End;
             }
             return result;
         }

src/Markdig/Extensions/Footnotes/Footnote.cs

@@ -34,6 +34,11 @@ namespace Markdig.Extensions.Footnotes
         /// </summary>
         public List<FootnoteLink> Links { get; private set; }
 
+        /// <summary>
+        /// The label span
+        /// </summary>
+        public SourceSpan LabelSpan;
+
         internal bool IsLastLineEmpty { get; set; }
     }
 }

src/Markdig/Extensions/Footnotes/FootnoteParser.cs

@@ -36,7 +36,8 @@ namespace Markdig.Extensions.Footnotes
             var saved = processor.Column;
             string label;
             int start = processor.Start;
-            if (!LinkHelper.TryParseLabel(ref processor.Line, false, out label) || !label.StartsWith("^") || processor.CurrentChar != ':')
+            SourceSpan labelSpan;
+            if (!LinkHelper.TryParseLabel(ref processor.Line, false, out label, out labelSpan) || !label.StartsWith("^") || processor.CurrentChar != ':')
             {
                 processor.GoToColumn(saved);
                 return BlockState.None;
@@ -48,7 +49,11 @@ namespace Markdig.Extensions.Footnotes
 
             processor.NextChar(); // Skip ':'
 
-            var footnote = new Footnote(this) {Label = label};
+            var footnote = new Footnote(this)
+            {
+                Label = label,
+                LabelSpan = labelSpan,
+            };
 
             // Maintain a list of all footnotes at document level
             var footnotes = processor.Document.GetData(DocumentKey) as FootnoteGroup;

src/Markdig/Extensions/GenericAttributes/GenericAttributesExtension.cs

@@ -62,8 +62,8 @@ namespace Markdig.Extensions.GenericAttributes
                         // Update position for HtmlAttributes
                         htmlAttributes.Line = processor.LineIndex;
                         htmlAttributes.Column = startOfAttributes - processor.CurrentLineStartPosition; // This is not accurate with tabs!
-                        htmlAttributes.SourceStartPosition = startOfAttributes;
-                        htmlAttributes.SourceEndPosition = copy.Start - 1;
+                        htmlAttributes.Span.Start = startOfAttributes;
+                        htmlAttributes.Span.End = copy.Start - 1;
 
                         line.End = indexOfAttributes - 1;
                         return true;

src/Markdig/Extensions/GenericAttributes/GenericAttributesParser.cs

@@ -69,10 +69,10 @@ namespace Markdig.Extensions.GenericAttributes
                 // Update the position of the attributes
                 int line;
                 int column;
-                currentHtmlAttributes.SourceStartPosition = processor.GetSourcePosition(startPosition, out line, out column);
+                currentHtmlAttributes.Span.Start = processor.GetSourcePosition(startPosition, out line, out column);
                 currentHtmlAttributes.Line = line;
                 currentHtmlAttributes.Column = column;
-                currentHtmlAttributes.SourceEndPosition = currentHtmlAttributes.SourceStartPosition + slice.Start - startPosition - 1;
+                currentHtmlAttributes.Span.End = currentHtmlAttributes.Span.Start + slice.Start - startPosition - 1;
 
                 // We don't set the processor.Inline as we don't want to add attach attributes to a particular entity
                 return true;

src/Markdig/Extensions/Mathematics/MathInlineParser.cs

@@ -5,6 +5,7 @@
 using Markdig.Helpers;
 using Markdig.Parsers;
 using Markdig.Renderers.Html;
+using Markdig.Syntax;
 
 namespace Markdig.Extensions.Mathematics
 {
@@ -106,8 +107,7 @@ namespace Markdig.Extensions.Mathematics
                 int column;
                 var inline = new MathInline()
                 {
-                    SourceStartPosition = processor.GetSourcePosition(startPosition, out line, out column),
-                    SourceEndPosition = processor.GetSourcePosition(slice.End),
+                    Span = new SourceSpan(processor.GetSourcePosition(startPosition, out line, out column), processor.GetSourcePosition(slice.End)),
                     Line = line,
                     Column = column,
                     Delimiter = match,

src/Markdig/Extensions/SmartyPants/SmaryPantsInlineParser.cs

@@ -167,13 +167,13 @@ namespace Markdig.Extensions.SmartyPants
             int column;
             var pant = new SmartyPant()
             {
-                SourceStartPosition = processor.GetSourcePosition(startingPosition, out line, out column),
+                Span = {Start = processor.GetSourcePosition(startingPosition, out line, out column)},
                 Line = line,
                 Column = column,
                 OpeningCharacter = openingChar,
                 Type = type
             };
-            pant.SourceEndPosition = pant.SourceStartPosition + slice.Start - startingPosition - 1;
+            pant.Span.End = pant.Span.Start + slice.Start - startingPosition - 1;
 
             // We will check in a post-process step for balanaced open/close quotes
             if (postProcess)
@@ -258,8 +258,7 @@ namespace Markdig.Extensions.SmartyPants
                             pants.RemoveAt(j);
                             toReplace.ReplaceBy(new LiteralInline(toReplace.ToString())
                             {
-                                SourceStartPosition = toReplace.SourceStartPosition,
-                                SourceEndPosition = toReplace.SourceEndPosition,
+                                Span = toReplace.Span,
                                 Line = toReplace.Line,
                                 Column = toReplace.Column,
                             });
@@ -282,8 +281,7 @@ namespace Markdig.Extensions.SmartyPants
             {
                 quote.ReplaceBy(new LiteralInline(quote.ToString())
                 {
-                    SourceStartPosition = quote.SourceStartPosition,
-                    SourceEndPosition = quote.SourceEndPosition,
+                    Span = quote.Span,
                     Line = quote.Line,
                     Column = quote.Column,
                 });

src/Markdig/Extensions/Tables/PipeTableParser.cs

@@ -102,8 +102,7 @@ namespace Markdig.Extensions.Tables
             {
                 processor.Inline = new PiprTableDelimiterInline(this)
                 {
-                    SourceStartPosition = position,
-                    SourceEndPosition = position,
+                    Span = new SourceSpan(position, position),
                     Line = globalLineIndex,
                     Column = column,
                     LocalLineIndex = localLineIndex
@@ -236,8 +235,8 @@ namespace Markdig.Extensions.Tables
             }
 
             // TODO: This is not accurate for the table
-            table.SourceStartPosition = column.SourceStartPosition;
-            table.SourceEndPosition = column.SourceEndPosition;
+            table.Span.Start = column.Span.Start;
+            table.Span.End = column.Span.End;
             table.Line = column.Line;
             table.Column = column.Column;
             
@@ -287,17 +286,16 @@ namespace Markdig.Extensions.Tables
                             {
                                 cellContainer.Line = item.Line;
                                 cellContainer.Column = item.Column;
-                                cellContainer.SourceStartPosition = item.SourceStartPosition;
+                                cellContainer.Span.Start = item.Span.Start;
                                 isFirstItem = false;
                             }
-                            cellContainer.SourceEndPosition = item.SourceEndPosition;
+                            cellContainer.Span.End = item.Span.End;
                             item = nextSibling;
                         }
 
                         var tableParagraph = new ParagraphBlock()
                         {
-                            SourceStartPosition = cellContainer.SourceStartPosition,
-                            SourceEndPosition = cellContainer.SourceEndPosition,
+                            Span = cellContainer.Span,
                             Line = cellContainer.Line,
                             Column = cellContainer.Column,
                             Inline = cellContainer
@@ -305,8 +303,7 @@ namespace Markdig.Extensions.Tables
 
                         var tableCell = new TableCell()
                         {
-                            SourceStartPosition = cellContainer.SourceStartPosition,
-                            SourceEndPosition = cellContainer.SourceEndPosition,
+                            Span = cellContainer.Span,
                             Line = cellContainer.Line,
                             Column = cellContainer.Column,
                         };
@@ -317,8 +314,7 @@ namespace Markdig.Extensions.Tables
                         {
                             row = new TableRow()
                             {
-                                SourceStartPosition = cellContainer.SourceStartPosition,
-                                SourceEndPosition = cellContainer.SourceEndPosition,
+                                Span = cellContainer.Span,
                                 Line = cellContainer.Line,
                                 Column = cellContainer.Column,
                             };

src/Markdig/Extensions/TaskLists/HtmlTaskListRenderer.cs

@@ -0,0 +1,35 @@
+// Copyright (c) Alexandre Mutel. All rights reserved.
+// This file is licensed under the BSD-Clause 2 license. 
+// See the license.txt file in the project root for more information.
+using System;
+using Markdig.Renderers;
+using Markdig.Renderers.Html;
+
+namespace Markdig.Extensions.TaskLists
+{
+    /// <summary>
+    /// A HTML renderer for a <see cref="TaskList"/>.
+    /// </summary>
+    /// <seealso cref="Markdig.Renderers.Html.HtmlObjectRenderer{TaskList}" />
+    public class HtmlTaskListRenderer : HtmlObjectRenderer<TaskList>
+    {
+        protected override void Write(HtmlRenderer renderer, TaskList obj)
+        {
+            if (renderer.EnableHtmlForInline)
+            {
+                renderer.Write("<input").WriteAttributes(obj).Write(" disabled=\"disabled\" type=\"checkbox\"");
+                if (obj.Checked)
+                {
+                    renderer.Write(" checked=\"checked\"");
+                }
+                renderer.Write(" />");
+            }
+            else
+            {
+                renderer.Write('[');
+                renderer.Write(obj.Checked ? "x" : " ");
+                renderer.Write(']');
+            }
+        }
+    }
+}

src/Markdig/Extensions/TaskLists/TaskList.cs

@@ -0,0 +1,17 @@
+// Copyright (c) Alexandre Mutel. All rights reserved.
+// This file is licensed under the BSD-Clause 2 license. 
+// See the license.txt file in the project root for more information.
+using System.Diagnostics;
+using Markdig.Syntax.Inlines;
+
+namespace Markdig.Extensions.TaskLists
+{
+    /// <summary>
+    /// An inline for TaskList.
+    /// </summary>
+    [DebuggerDisplay("TaskList {Checked}")]
+    public class TaskList : LeafInline
+    {
+        public bool Checked { get; set; }
+    }
+}

src/Markdig/Extensions/TaskLists/TaskListExtension.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Alexandre Mutel. All rights reserved.
+// This file is licensed under the BSD-Clause 2 license. 
+// See the license.txt file in the project root for more information.
+
+using Markdig.Parsers.Inlines;
+using Markdig.Renderers;
+
+namespace Markdig.Extensions.TaskLists
+{
+    /// <summary>
+    /// Extension to enable TaskList.
+    /// </summary>
+    public class TaskListExtension : IMarkdownExtension
+    {
+        public void Setup(MarkdownPipelineBuilder pipeline)
+        {
+            if (!pipeline.InlineParsers.Contains<TaskListInlineParser>())
+            {
+                // Insert the parser after the code span parser
+                pipeline.InlineParsers.InsertBefore<LinkInlineParser>(new TaskListInlineParser());
+            }
+        }
+
+        public void Setup(IMarkdownRenderer renderer)
+        {
+            var htmlRenderer = renderer as HtmlRenderer;
+            if (htmlRenderer != null)
+            {
+                htmlRenderer.ObjectRenderers.AddIfNotAlready<HtmlTaskListRenderer>();
+            }
+        }
+    }
+}

src/Markdig/Extensions/TaskLists/TaskListInlineParser.cs

@@ -0,0 +1,62 @@
+// Copyright (c) Alexandre Mutel. All rights reserved.
+// This file is licensed under the BSD-Clause 2 license. 
+// See the license.txt file in the project root for more information.
+using Markdig.Helpers;
+using Markdig.Parsers;
+using Markdig.Syntax;
+
+namespace Markdig.Extensions.TaskLists
+{
+    /// <summary>
+    /// The inline parser for SmartyPants.
+    /// </summary>
+    public class TaskListInlineParser : InlineParser
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="TaskListInlineParser"/> class.
+        /// </summary>
+        public TaskListInlineParser()
+        {
+            OpeningCharacters = new[] {'['};
+        }
+
+        public override bool Match(InlineProcessor processor, ref StringSlice slice)
+        {
+            // A tasklist is either
+            // [ ]
+            // or [x] or [X]
+
+            if (!(processor.Block.Parent is ListItemBlock))
+            {
+                return false;
+            }
+
+            var startingPosition = slice.Start;
+            var c = slice.NextChar();
+            if (!c.IsSpace() && c != 'x' && c != 'X')
+            {
+                return false;
+            }
+            if (slice.NextChar() != ']')
+            {
+                return false;
+            }
+            // Skip last ]
+            slice.NextChar();
+
+            // Create the TaskList
+            int line;
+            int column;
+            var taskItem = new TaskList()
+            {
+                Span = { Start = processor.GetSourcePosition(startingPosition, out line, out column)},
+                Line = line,
+                Column = column,
+                Checked = !c.IsSpace()
+            };
+            taskItem.Span.End = taskItem.Span.Start + 2;
+            processor.Inline = taskItem;
+            return true;
+        }
+    }
+}

src/Markdig/Helpers/LinkHelper.cs

@@ -297,10 +297,24 @@ namespace Markdig.Helpers
 
         public static bool TryParseInlineLink(StringSlice text, out string link, out string title)
         {
-            return TryParseInlineLink(ref text, out link, out title);
+            SourceSpan linkSpan;
+            SourceSpan titleSpan;
+            return TryParseInlineLink(ref text, out link, out title, out linkSpan, out titleSpan);
+        }
+
+        public static bool TryParseInlineLink(StringSlice text, out string link, out string title, out SourceSpan linkSpan, out SourceSpan titleSpan)
+        {
+            return TryParseInlineLink(ref text, out link, out title, out linkSpan, out titleSpan);
         }
 
         public static bool TryParseInlineLink(ref StringSlice text, out string link, out string title)
+        {
+            SourceSpan linkSpan;
+            SourceSpan titleSpan;
+            return TryParseInlineLink(ref text, out link, out title, out linkSpan, out titleSpan);
+        }
+
+        public static bool TryParseInlineLink(ref StringSlice text, out string link, out string title, out SourceSpan linkSpan, out SourceSpan titleSpan)
         {
             // 1. An inline link consists of a link text followed immediately by a left parenthesis (, 
             // 2. optional whitespace,  TODO: specs: is it whitespace or multiple whitespaces?
@@ -313,14 +327,25 @@ namespace Markdig.Helpers
             link = null;
             title = null;
 
+            linkSpan = SourceSpan.Empty;
+            titleSpan = SourceSpan.Empty;
+
             // 1. An inline link consists of a link text followed immediately by a left parenthesis (, 
             if (c == '(')
             {
                 text.NextChar();
                 text.TrimStart();
 
+                var pos = text.Start;
                 if (TryParseUrl(ref text, out link))
                 {
+                    linkSpan.Start = pos;
+                    linkSpan.End = text.Start - 1;
+                    if (linkSpan.End < linkSpan.Start)
+                    {
+                        linkSpan = SourceSpan.Empty;
+                    }
+
                     int spaceCount;
                     text.TrimStart(out spaceCount);
                     var hasWhiteSpaces = spaceCount > 0;
@@ -333,12 +358,19 @@ namespace Markdig.Helpers
                     else if (hasWhiteSpaces)
                     {
                         c = text.CurrentChar;
+                        pos = text.Start;
                         if (c == ')')
                         {
                             isValid = true;
                         }
                         else if (TryParseTitle(ref text, out title))
                         {
+                            titleSpan.Start = pos;
+                            titleSpan.End = text.Start - 1;
+                            if (titleSpan.End < titleSpan.Start)
+                            {
+                                titleSpan = SourceSpan.Empty;
+                            }
                             text.TrimStart();
                             c = text.CurrentChar;
 
@@ -582,12 +614,25 @@ namespace Markdig.Helpers
             return TryParseLinkReferenceDefinition(ref text, out label, out url, out title);
         }
 
-        public static bool TryParseLinkReferenceDefinition<T>(ref T text, out string label, out string url, 
-            out string title) where T : ICharIterator
+        public static bool TryParseLinkReferenceDefinition<T>(ref T text, out string label, out string url, out string title)
+            where T : ICharIterator
+        {
+            SourceSpan labelSpan;
+            SourceSpan urlSpan;
+            SourceSpan titleSpan;
+            return TryParseLinkReferenceDefinition(ref text, out label, out url, out title, out labelSpan, out urlSpan,
+                out titleSpan);
+        }
+
+        public static bool TryParseLinkReferenceDefinition<T>(ref T text, out string label, out string url, out string title, out SourceSpan labelSpan, out SourceSpan urlSpan, out SourceSpan titleSpan) where T : ICharIterator
         {
             url = null;
             title = null;
-            if (!TryParseLabel(ref text, out label))
+
+            urlSpan = SourceSpan.Empty;
+            titleSpan = SourceSpan.Empty;
+
+            if (!TryParseLabel(ref text, out label, out labelSpan))
             {
                 return false;
             }
@@ -601,10 +646,13 @@ namespace Markdig.Helpers
 
             // Skip any whitespaces before the url
             text.TrimStart();
+
+            urlSpan.Start = text.Start;
             if (!TryParseUrl(ref text, out url) || string.IsNullOrEmpty(url))
             {
                 return false;
             }
+            urlSpan.End = text.Start - 1;
 
             var saved = text;
             int newLineCount;
@@ -612,8 +660,10 @@ namespace Markdig.Helpers
             var c = text.CurrentChar;
             if (c == '\'' || c == '"' || c == '(')
             {
+                titleSpan.Start = text.Start;
                 if (TryParseTitle(ref text, out title))
                 {
+                    titleSpan.End = text.Start - 1;
                     // If we have a title, it requires a whitespace after the url
                     if (!hasWhiteSpaces)
                     {
@@ -662,24 +712,41 @@ namespace Markdig.Helpers
 
         public static bool TryParseLabel<T>(T lines, out string label) where T : ICharIterator
         {
-            return TryParseLabel(ref lines, false, out label);
+            SourceSpan labelSpan;
+            return TryParseLabel(ref lines, false, out label, out labelSpan);
+        }
+
+        public static bool TryParseLabel<T>(T lines, out string label, out SourceSpan labelSpan) where T : ICharIterator
+        {
+            return TryParseLabel(ref lines, false, out label, out labelSpan);
         }
 
         public static bool TryParseLabel<T>(ref T lines, out string label) where T : ICharIterator
         {
-            return TryParseLabel(ref lines, false, out label);
+            SourceSpan labelSpan;
+            return TryParseLabel(ref lines, false, out label, out labelSpan);
         }
 
-        public static bool TryParseLabel<T>(ref T lines, bool allowEmpty, out string label) where T : ICharIterator
+
+        public static bool TryParseLabel<T>(ref T lines, out string label, out SourceSpan labelSpan) where T : ICharIterator
+        {
+            return TryParseLabel(ref lines, false, out label, out labelSpan);
+        }
+
+        public static bool TryParseLabel<T>(ref T lines, bool allowEmpty, out string label, out SourceSpan labelSpan) where T : ICharIterator
         {
             label = null;
             char c = lines.CurrentChar;
+            labelSpan = SourceSpan.Empty;
             if (c != '[')
             {
                 return false;
             }
             var buffer = StringBuilderCache.Local();
 
+            var startLabel = -1;
+            var endLabel = -1;
+
             bool hasEscape = false;
             bool previousWhitespace = true;
             bool hasNonWhiteSpace = false;
@@ -719,11 +786,19 @@ namespace Markdig.Helpers
                                     break;
                                 }
                                 buffer.Length = i;
+                                endLabel--;
                             }
 
                             // Only valid if buffer is less than 1000 characters
                             if (buffer.Length <= 999)
                             {
+                                labelSpan.Start = startLabel;
+                                labelSpan.End = endLabel;
+                                if (labelSpan.Start > labelSpan.End)
+                                {
+                                    labelSpan = SourceSpan.Empty;
+                                }
+
                                 label = buffer.ToString();
                                 isValid = true;
                             }
@@ -741,6 +816,10 @@ namespace Markdig.Helpers
 
                 if (!hasEscape && c == '\\')
                 {
+                    if (startLabel < 0)
+                    {
+                        startLabel = lines.Start;
+                    }
                     hasEscape = true;
                 }
                 else
@@ -749,6 +828,11 @@ namespace Markdig.Helpers
 
                     if (!previousWhitespace || !isWhitespace)
                     {
+                        if (startLabel < 0)
+                        {
+                            startLabel = lines.Start;
+                        }
+                        endLabel = lines.Start;
                         buffer.Append(c);
                         if (!isWhitespace)
                         {

src/Markdig/MarkdownExtensions.cs

@@ -21,6 +21,7 @@ using Markdig.Extensions.Mathematics;
 using Markdig.Extensions.MediaLinks;
 using Markdig.Extensions.SmartyPants;
 using Markdig.Extensions.Tables;
+using Markdig.Extensions.TaskLists;
 using Markdig.Parsers;
 using Markdig.Parsers.Inlines;
 
@@ -53,6 +54,7 @@ namespace Markdig
                 .UseMediaLinks()
                 .UsePipeTables()
                 .UseListExtras()
+                .UseTaskLists()
                 .UseGenericAttributes(); // Must be last as it is one parser that is modifying other parsers
         }
 
@@ -67,6 +69,17 @@ namespace Markdig
             return pipeline;
         }
 
+        /// <summary>
+        /// Uses the task list extension.
+        /// </summary>
+        /// <param name="pipeline">The pipeline.</param>
+        /// <returns>The modified pipeline</returns>
+        public static MarkdownPipelineBuilder UseTaskLists(this MarkdownPipelineBuilder pipeline)
+        {
+            pipeline.Extensions.AddIfNotAlready<TaskListExtension>();
+            return pipeline;
+        }
+
         /// <summary>
         /// Uses the custom container extension.
         /// </summary>
@@ -407,6 +420,9 @@ namespace Markdig
                     case "autoidentifiers":
                         pipeline.UseAutoIdentifiers();
                         break;
+                    case "tasklists":
+                        pipeline.UseTaskLists();
+                        break;
                     default:
                         throw new ArgumentException($"unknown extension {extension}");
                 }

src/Markdig/Parsers/BlockProcessor.cs

@@ -590,8 +590,16 @@ namespace Markdig.Parsers
         /// </summary>
         private void TryOpenBlocks()
         {
+            int previousStart = -1;
             while (ContinueProcessingLine)
             {
+                // Security check so that the parser can't go into a crazy infinite loop if one extension is messing
+                if (previousStart == Start)
+                {
+                    throw new InvalidOperationException($"The parser is in an invalid infinite loop while trying to parse blocks at line [{LineIndex}] with line [{Line}]");
+                }
+                previousStart = Start;
+
                 // Eat indent spaces before checking the character
                 ParseIndent();
 

src/Markdig/Parsers/FencedBlockParserBase.cs

@@ -159,8 +159,8 @@ namespace Markdig.Parsers
                 fenced.Column = processor.Column;
                 fenced.FencedChar = matchChar;
                 fenced.FencedCharCount = count;
-                fenced.SourceStartPosition = startPosition;
-                fenced.SourceEndPosition = line.Start;
+                fenced.Span.Start = startPosition;
+                fenced.Span.End = line.Start;
             };
 
             // Try to parse any attached attributes
@@ -216,7 +216,7 @@ namespace Markdig.Parsers
             // The line must contain only fence opening character followed only by whitespaces.
             if (count <=0 && !processor.IsCodeIndent && (c == '\0' || c.IsWhitespace()) && line.TrimEnd())
             {
-                block.SourceEndPosition = line.Start - 1;
+                block.Span.End = line.Start - 1;
 
                 // Don't keep the last line
                 return BlockState.BreakDiscard;

src/Markdig/Parsers/HeadingBlockParser.cs

@@ -70,7 +70,7 @@ namespace Markdig.Parsers
                     HeaderChar = matchingChar,
                     Level = leadingCount,
                     Column = column,
-                    SourceStartPosition =  sourcePosition
+                    Span = { Start =  sourcePosition }
                 };
                 processor.NewBlocks.Push(headingBlock);
                 processor.GoToColumn(column + leadingCount + 1);
@@ -119,7 +119,7 @@ namespace Markdig.Parsers
                 }
 
                 // Setup the source end position of this element
-                headingBlock.SourceEndPosition = processor.Line.End;
+                headingBlock.Span.End = processor.Line.End;
 
                 // We expect a single line, so don't continue
                 return BlockState.Break;

src/Markdig/Parsers/HtmlBlockParser.cs

@@ -185,35 +185,35 @@ namespace Markdig.Parsers
                 case HtmlBlockType.Comment:
                     if (line.Search("-->", out endof))
                     {
-                        htmlBlock.SourceEndPosition = endof - 1;
+                        htmlBlock.Span.End = endof - 1;
                         result = BlockState.Break;
                     }
                     break;
                 case HtmlBlockType.CData:
                     if (line.Search("]]>", out endof))
                     {
-                        htmlBlock.SourceEndPosition = endof - 1;
+                        htmlBlock.Span.End = endof - 1;
                         result = BlockState.Break;
                     }
                     break;
                 case HtmlBlockType.ProcessingInstruction:
                     if (line.Search("?>", out endof))
                     {
-                        htmlBlock.SourceEndPosition = endof - 1;
+                        htmlBlock.Span.End = endof - 1;
                         result = BlockState.Break;
                     }
                     break;
                 case HtmlBlockType.DocumentType:
                     if (line.Search(">", out endof))
                     {
-                        htmlBlock.SourceEndPosition = endof - 1;
+                        htmlBlock.Span.End = endof - 1;
                         result = BlockState.Break;
                     }
                     break;
                 case HtmlBlockType.ScriptPreOrStyle:
                     if (line.SearchLowercase("</script>", out endof) || line.SearchLowercase("</pre>", out endof) || line.SearchLowercase("</style>", out endof))
                     {
-                        htmlBlock.SourceEndPosition = endof - 1;
+                        htmlBlock.Span.End = endof - 1;
                         result = BlockState.Break;
                     }
                     break;
@@ -234,7 +234,7 @@ namespace Markdig.Parsers
             // Update only if we don't have a break discard
             if (result != BlockState.BreakDiscard)
             {
-                htmlBlock.SourceEndPosition = line.End;
+                htmlBlock.Span.End = line.End;
             }
 
             return result;
@@ -246,9 +246,8 @@ namespace Markdig.Parsers
             {
                 Column = startColumn,
                 Type = type,
-                SourceStartPosition = startPosition,
                 // By default, setup to the end of line
-                SourceEndPosition = startPosition + state.Line.End
+                Span = new SourceSpan(startPosition, startPosition + state.Line.End)
             });
             return BlockState.Continue;
         }

src/Markdig/Parsers/IndentedCodeBlockParser.cs

@@ -25,8 +25,7 @@ namespace Markdig.Parsers
                 processor.NewBlocks.Push(new CodeBlock(this)
                 {
                     Column = processor.Column,
-                    SourceStartPosition = startPosition,
-                    SourceEndPosition = processor.Line.End
+                    Span = new SourceSpan(startPosition, processor.Line.End)
                 });
             }
             return result;
@@ -49,7 +48,7 @@ namespace Markdig.Parsers
             }
             if (block != null)
             {
-                block.SourceEndPosition = processor.Line.End;
+                block.Span.End = processor.Line.End;
             }
             return BlockState.Continue;
         }

src/Markdig/Parsers/InlineProcessor.cs

@@ -119,6 +119,18 @@ namespace Markdig.Parsers
             return GetSourcePosition(sliceOffset, out lineIndex, out column);
         }
 
+        public SourceSpan GetSourcePositionFromLocalSpan(SourceSpan span)
+        {
+            if (span.IsEmpty)
+            {
+                return SourceSpan.Empty;
+            }
+
+            int column;
+            int lineIndex;
+            return new SourceSpan(GetSourcePosition(span.Start, out lineIndex, out column), GetSourcePosition(span.End, out lineIndex, out column));
+        }
+
         /// <summary>
         /// Gets the source position for the specified offset within the current slice.
         /// </summary>
@@ -159,6 +171,8 @@ namespace Markdig.Parsers
         /// <param name="leafBlock">The leaf block.</param>
         public void ProcessInlineLeaf(LeafBlock leafBlock)
         {
+            if (leafBlock == null) throw new ArgumentNullException(nameof(leafBlock));
+
             // clear parser states
             Array.Clear(ParserStates, 0, ParserStates.Length);
 
@@ -175,8 +189,17 @@ namespace Markdig.Parsers
             var text = leafBlock.Lines.ToSlice(lineOffsets);
             leafBlock.Lines = new StringLineGroup();
 
+            int previousStart = -1;
+
             while (!text.IsEmpty)
             {
+                // Security check so that the parser can't go into a crazy infinite loop if one extension is messing
+                if (previousStart == text.Start)
+                {
+                    throw new InvalidOperationException($"The parser is in an invalid infinite loop while trying to parse inlines for block [{leafBlock.GetType().Name}] at position ({leafBlock.ToPositionText()}");
+                }
+                previousStart = text.Start;
+
                 var c = text.CurrentChar;
 
                 var textSaved = text;

src/Markdig/Parsers/Inlines/AutolineInlineParser.cs

@@ -2,6 +2,7 @@
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 using Markdig.Helpers;
+using Markdig.Syntax;
 using Markdig.Syntax.Inlines;
 
 namespace Markdig.Parsers.Inlines
@@ -39,8 +40,7 @@ namespace Markdig.Parsers.Inlines
                 {
                     IsEmail = isEmail,
                     Url = link,
-                    SourceStartPosition = processor.GetSourcePosition(saved.Start, out line, out column),
-                    SourceEndPosition = processor.GetSourcePosition(slice.Start - 1),
+                    Span = new SourceSpan(processor.GetSourcePosition(saved.Start, out line, out column), processor.GetSourcePosition(slice.Start - 1)),
                     Line = line,
                     Column = column
                 };
@@ -57,8 +57,7 @@ namespace Markdig.Parsers.Inlines
                 processor.Inline = new HtmlInline()
                 {
                     Tag = htmlTag,
-                    SourceStartPosition = processor.GetSourcePosition(saved.Start, out line, out column),
-                    SourceEndPosition = processor.GetSourcePosition(slice.Start - 1),
+                    Span = new SourceSpan(processor.GetSourcePosition(saved.Start, out line, out column), processor.GetSourcePosition(slice.Start - 1)),
                     Line = line,
                     Column = column
                 };

src/Markdig/Parsers/Inlines/CodeInlineParser.cs

@@ -2,6 +2,7 @@
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 using Markdig.Helpers;
+using Markdig.Syntax;
 using Markdig.Syntax.Inlines;
 
 namespace Markdig.Parsers.Inlines
@@ -106,8 +107,7 @@ namespace Markdig.Parsers.Inlines
                 {
                     Delimiter = match,
                     Content = builder.ToString(),
-                    SourceStartPosition = processor.GetSourcePosition(startPosition, out line, out column),
-                    SourceEndPosition = processor.GetSourcePosition(slice.Start - 1),
+                    Span = new SourceSpan(processor.GetSourcePosition(startPosition, out line, out column), processor.GetSourcePosition(slice.Start - 1)),
                     Line = line,
                     Column = column
                 };

src/Markdig/Parsers/Inlines/EmphasisInlineParser.cs

@@ -185,8 +185,7 @@ namespace Markdig.Parsers.Inlines
                 {
                     DelimiterCount = delimiterCount,
                     Type = delimiterType,
-                    SourceStartPosition = processor.GetSourcePosition(startPosition, out line, out column),
-                    SourceEndPosition = processor.GetSourcePosition(slice.Start - 1),
+                    Span = new SourceSpan(processor.GetSourcePosition(startPosition, out line, out column), processor.GetSourcePosition(slice.Start - 1)),
                     Column = column,
                     Line = line,
                 };
@@ -254,14 +253,14 @@ namespace Markdig.Parsers.Inlines
                             var closeDelimitercount = closeDelimiter.DelimiterCount;
                             var delimiterDelta = isStrong ? 2 : 1;
 
-                            emphasis.SourceStartPosition = openDelimiter.SourceStartPosition;
+                            emphasis.Span.Start = openDelimiter.Span.Start;
                             emphasis.Line = openDelimiter.Line;
                             emphasis.Column = openDelimiter.Column;
-                            emphasis.SourceEndPosition = closeDelimiter.SourceEndPosition - closeDelimitercount + delimiterDelta;
+                            emphasis.Span.End = closeDelimiter.Span.End - closeDelimitercount + delimiterDelta;
 
-                            openDelimiter.SourceStartPosition += delimiterDelta;
+                            openDelimiter.Span.Start += delimiterDelta;
                             openDelimiter.Column += delimiterDelta;
-                            closeDelimiter.SourceStartPosition += delimiterDelta;
+                            closeDelimiter.Span.Start += delimiterDelta;
                             closeDelimiter.Column += delimiterDelta;
 
                             openDelimiter.DelimiterCount -= delimiterDelta;
@@ -301,8 +300,7 @@ namespace Markdig.Parsers.Inlines
                                 {
                                     Content = new StringSlice(literalDelimiter.ToLiteral()),
                                     IsClosed = true,
-                                    SourceStartPosition = literalDelimiter.SourceStartPosition,
-                                    SourceEndPosition = literalDelimiter.SourceEndPosition,
+                                    Span = literalDelimiter.Span,
                                     Line = literalDelimiter.Line,
                                     Column = literalDelimiter.Column
                                 };
@@ -355,8 +353,7 @@ namespace Markdig.Parsers.Inlines
                             {
                                 Content = new StringSlice(closeDelimiter.ToLiteral()),
                                 IsClosed = true,
-                                SourceStartPosition = closeDelimiter.SourceStartPosition,
-                                SourceEndPosition = closeDelimiter.SourceEndPosition,
+                                Span = closeDelimiter.Span,
                                 Line = closeDelimiter.Line,
                                 Column = closeDelimiter.Column
                             };
@@ -383,8 +380,7 @@ namespace Markdig.Parsers.Inlines
                 {
                     Content = new StringSlice(delimiter.ToLiteral()),
                     IsClosed = true,
-                    SourceStartPosition = delimiter.SourceStartPosition,
-                    SourceEndPosition = delimiter.SourceEndPosition,
+                    Span = delimiter.Span,
                     Line = delimiter.Line,
                     Column = delimiter.Column
                 };

src/Markdig/Parsers/Inlines/EscapeInlineParser.cs

@@ -29,11 +29,11 @@ namespace Markdig.Parsers.Inlines
                 processor.Inline = new LiteralInline()
                 {
                     Content = new StringSlice(new string(c, 1)),
-                    SourceStartPosition = processor.GetSourcePosition(startPosition, out line, out column),
+                    Span = { Start = processor.GetSourcePosition(startPosition, out line, out column) },
                     Line = line,
                     Column = column
                 };
-                processor.Inline.SourceEndPosition = processor.Inline.SourceStartPosition + 1;
+                processor.Inline.Span.End = processor.Inline.Span.Start + 1;
                 slice.NextChar();
                 return true;
             }
@@ -44,11 +44,11 @@ namespace Markdig.Parsers.Inlines
                 processor.Inline = new LineBreakInline()
                 {
                     IsHard = true,
-                    SourceStartPosition = processor.GetSourcePosition(startPosition, out line, out column),
+                    Span = { Start = processor.GetSourcePosition(startPosition, out line, out column) },
                     Line = line,
                     Column = column
                 };
-                processor.Inline.SourceEndPosition = processor.Inline.SourceStartPosition + 1;
+                processor.Inline.Span.End = processor.Inline.Span.Start + 1;
                 slice.NextChar();
                 return true;
             }

src/Markdig/Parsers/Inlines/HtmlEntityParser.cs

@@ -2,6 +2,7 @@
 // This file is licensed under the BSD-Clause 2 license. 
 // See the license.txt file in the project root for more information.
 using Markdig.Helpers;
+using Markdig.Syntax;
 using Markdig.Syntax.Inlines;
 
 namespace Markdig.Parsers.Inlines
@@ -51,8 +52,7 @@ namespace Markdig.Parsers.Inlines
                 {
                     Original = matched,
                     Transcoded = new StringSlice(literal),
-                    SourceStartPosition = processor.GetSourcePosition(startPosition, out line, out column),
-                    SourceEndPosition = processor.GetSourcePosition(matched.End + 1),
+                    Span = new SourceSpan(processor.GetSourcePosition(startPosition, out line, out column), processor.GetSourcePosition(matched.End + 1)),
                     Line = line,
                     Column = column
                 };

src/Markdig/Parsers/Inlines/LineBreakInlineParser.cs

@@ -42,12 +42,12 @@ namespace Markdig.Parsers.Inlines
             int column;
             processor.Inline = new LineBreakInline
             {
-                SourceStartPosition = processor.GetSourcePosition(startPosition, out line, out column),
+                Span = { Start = processor.GetSourcePosition(startPosition, out line, out column)},
                 IsHard = EnableSoftAsHard || (slice.Start != 0 && hasDoubleSpacesBefore),
                 Line = line,
                 Column = column
             };
-            processor.Inline.SourceEndPosition = processor.Inline.SourceStartPosition;
+            processor.Inline.Span.End = processor.Inline.Span.Start;
             return true;
         }
     }

src/Markdig/Parsers/Inlines/LinkInlineParser.cs

@@ -51,8 +51,9 @@ namespace Markdig.Parsers.Inlines
                     var saved = slice;
                     string label;
 
+                    SourceSpan labelSpan;
                     // If the label is followed by either a ( or a [, this is not a shortcut
-                    if (LinkHelper.TryParseLabel(ref slice, out label))
+                    if (LinkHelper.TryParseLabel(ref slice, out label, out labelSpan))
                     {
                         if (!processor.Document.ContainsLinkReferenceDefinition(label))
                         {
@@ -67,9 +68,9 @@ namespace Markdig.Parsers.Inlines
                     {
                         Type = DelimiterType.Open,
                         Label = label,
+                        LabelSpan = processor.GetSourcePositionFromLocalSpan(labelSpan),
                         IsImage = isImage,
-                        SourceStartPosition = startPosition,
-                        SourceEndPosition = processor.GetSourcePosition(slice.Start - 1),
+                        Span = new SourceSpan(startPosition, processor.GetSourcePosition(slice.Start - 1)),
                         Line = line,
                         Column = column
                     };
@@ -94,7 +95,7 @@ namespace Markdig.Parsers.Inlines
             return false;
         }
 
-        private bool ProcessLinkReference(InlineProcessor state, string label, LinkDelimiterInline parent, int endPosition)
+        private bool ProcessLinkReference(InlineProcessor state, string label, SourceSpan labelSpan, LinkDelimiterInline parent, int endPosition)
         {
             bool isValidLink = false;
             LinkReferenceDefinition linkRef;
@@ -115,9 +116,11 @@ namespace Markdig.Parsers.Inlines
                     {
                         Url = HtmlHelper.Unescape(linkRef.Url),
                         Title = HtmlHelper.Unescape(linkRef.Title),
+                        Label = label,
+                        LabelSpan = labelSpan,
                         IsImage = parent.IsImage,
-                        SourceStartPosition = parent.SourceStartPosition,
-                        SourceEndPosition = endPosition,
+                        Reference = linkRef,
+                        Span = new SourceSpan(parent.Span.Start, endPosition),
                         Line = parent.Line,
                         Column = parent.Column,
                     };
@@ -134,8 +137,7 @@ namespace Markdig.Parsers.Inlines
                             Content = new StringSlice(label),
                             IsClosed = true,
                             // Not exact but we leave it like this
-                            SourceStartPosition = parent.SourceStartPosition,
-                            SourceEndPosition = parent.SourceEndPosition,
+                            Span = parent.Span,
                             Line = parent.Line,
                             Column = parent.Column,
                         };
@@ -194,8 +196,7 @@ namespace Markdig.Parsers.Inlines
                     inlineState.Inline = new LiteralInline()
                     {
                         Content = new StringSlice("["),
-                        SourceStartPosition = openParent.SourceStartPosition,
-                        SourceEndPosition = openParent.SourceStartPosition,
+                        Span = openParent.Span,
                         Line = openParent.Line,
                         Column = openParent.Column,
                     };
@@ -214,7 +215,9 @@ namespace Markdig.Parsers.Inlines
                     case '(':
                         string url;
                         string title;
-                        if (LinkHelper.TryParseInlineLink(ref text, out url, out title))
+                        SourceSpan linkSpan;
+                        SourceSpan titleSpan;
+                        if (LinkHelper.TryParseInlineLink(ref text, out url, out title, out linkSpan, out titleSpan))
                         {
                             // Inline Link
                             var link = new LinkInline()
@@ -222,8 +225,10 @@ namespace Markdig.Parsers.Inlines
                                 Url = HtmlHelper.Unescape(url),
                                 Title = HtmlHelper.Unescape(title),
                                 IsImage = openParent.IsImage,
-                                SourceStartPosition = openParent.SourceStartPosition,
-                                SourceEndPosition = inlineState.GetSourcePosition(text.Start -1),
+                                LabelSpan = openParent.LabelSpan,
+                                UrlSpan = inlineState.GetSourcePositionFromLocalSpan(linkSpan),
+                                TitleSpan = inlineState.GetSourcePositionFromLocalSpan(titleSpan),
+                                Span = new SourceSpan(openParent.Span.Start, inlineState.GetSourcePosition(text.Start -1)),
                                 Line = openParent.Line,
                                 Column = openParent.Column,
                             };
@@ -250,13 +255,17 @@ namespace Markdig.Parsers.Inlines
                         break;
                     default:
 
+                        var labelSpan = SourceSpan.Empty;
                         string label = null;
+                        bool isLabelSpanLocal = true;
                         // Handle Collapsed links
                         if (text.CurrentChar == '[')
                         {
                             if (text.PeekChar(1) == ']')
                             {
                                 label = openParent.Label;
+                                labelSpan = openParent.LabelSpan;
+                                isLabelSpanLocal = false;
                                 text.NextChar(); // Skip [
                                 text.NextChar(); // Skip ]
                             }
@@ -266,9 +275,14 @@ namespace Markdig.Parsers.Inlines
                             label = openParent.Label;
                         }
 
-                        if (label != null || LinkHelper.TryParseLabel(ref text, true, out label))
+                        if (label != null || LinkHelper.TryParseLabel(ref text, true, out label, out labelSpan))
                         {
-                            if (ProcessLinkReference(inlineState, label, openParent, inlineState.GetSourcePosition(text.Start - 1)))
+                            if (isLabelSpanLocal)
+                            {
+                                labelSpan = inlineState.GetSourcePositionFromLocalSpan(labelSpan);
+                            }
+
+                            if (ProcessLinkReference(inlineState, label, labelSpan, openParent, inlineState.GetSourcePosition(text.Start - 1)))
                             {
                                 // Remove the open parent
                                 openParent.Remove();
@@ -292,6 +306,7 @@ namespace Markdig.Parsers.Inlines
 
                 var literal = new LiteralInline()
                 {
+                    Span = openParent.Span,
                     Content = new StringSlice(openParent.IsImage ? "![" : "[")
                 };
 

src/Markdig/Parsers/Inlines/LiteralInlineParser.cs

@@ -3,6 +3,7 @@
 // See the license.txt file in the project root for more information.
 
 using Markdig.Helpers;
+using Markdig.Syntax;
 using Markdig.Syntax.Inlines;
 
 namespace Markdig.Parsers.Inlines
@@ -67,8 +68,7 @@ namespace Markdig.Parsers.Inlines
             processor.Inline = new LiteralInline()
             {
                 Content = length > 0 ? new StringSlice(slice.Text, slice.Start, endPosition) : StringSlice.Empty,
-                SourceStartPosition = startPosition,
-                SourceEndPosition = processor.GetSourcePosition(endPosition),
+                Span = new SourceSpan(startPosition, processor.GetSourcePosition(endPosition)),
                 Line = line,
                 Column = column,
             };

src/Markdig/Parsers/ListBlockParser.cs

@@ -153,7 +153,7 @@ namespace Markdig.Parsers
                 }
 
                 // Update list-item source end position
-                listItem.SourceEndPosition = state.Line.End;
+                listItem.Span.End = state.Line.End;
                 
                 return BlockState.Continue;
             }
@@ -174,7 +174,7 @@ namespace Markdig.Parsers
                 }
 
                 // Update list-item source end position
-                listItem.SourceEndPosition = state.Line.End;
+                listItem.Span.End = state.Line.End;
 
                 return BlockState.Continue;
             }
@@ -258,8 +258,7 @@ namespace Markdig.Parsers
             {
                 Column = initColumn,
                 ColumnWidth = columnWidth,
-                SourceStartPosition = sourcePosition,
-                SourceEndPosition = sourceEndPosition
+                Span = new SourceSpan(sourcePosition, sourceEndPosition)
             };
             state.NewBlocks.Push(newListItem);
 
@@ -286,8 +285,7 @@ namespace Markdig.Parsers
                 var newList = new ListBlock(this)
                 {
                     Column = initColumn,
-                    SourceStartPosition = sourcePosition,
-                    SourceEndPosition = sourceEndPosition,
+                    Span = new SourceSpan(sourcePosition, sourceEndPosition),
                     IsOrdered = isOrdered,
                     BulletType = listInfo.BulletType,
                     OrderedDelimiter = listInfo.OrderedDelimiter,
@@ -357,7 +355,7 @@ namespace Markdig.Parsers
             // Update end-position for the list
             if (listBlock.Count > 0)
             {
-                listBlock.SourceEndPosition = listBlock[listBlock.Count - 1].SourceEndPosition;
+                listBlock.Span.End = listBlock[listBlock.Count - 1].Span.End;
             }
 
             return true;

src/Markdig/Parsers/ParagraphBlockParser.cs

@@ -23,8 +23,7 @@ namespace Markdig.Parsers
             processor.NewBlocks.Push(new ParagraphBlock(this)
             {
                 Column = processor.Column,
-                SourceStartPosition = processor.Line.Start,
-                SourceEndPosition = processor.Line.End
+                Span = new SourceSpan(processor.Line.Start, processor.Line.End)
             });
             return BlockState.Continue;
         }
@@ -41,7 +40,7 @@ namespace Markdig.Parsers
                 return TryParseSetexHeading(processor, block);
             }
 
-            block.SourceEndPosition = processor.Line.End;
+            block.Span.End = processor.Line.End;
             return BlockState.Continue;
         }
 
@@ -128,8 +127,7 @@ namespace Markdig.Parsers
                     var heading = new HeadingBlock(this)
                     {
                         Column = paragraph.Column,
-                        SourceStartPosition = paragraph.SourceStartPosition,
-                        SourceEndPosition = line.Start,
+                        Span = new SourceSpan(paragraph.Span.Start, line.Start),
                         Level = level,
                         Lines = paragraph.Lines,
                     };
@@ -141,7 +139,7 @@ namespace Markdig.Parsers
                 return BlockState.BreakDiscard;
             }
 
-            block.SourceEndPosition = state.Line.End;
+            block.Span.End = state.Line.End;
 
             return BlockState.Continue;
         }

src/Markdig/Parsers/QuoteBlockParser.cs

@@ -42,8 +42,7 @@ namespace Markdig.Parsers
             {
                 QuoteChar = quoteChar,
                 Column = column,
-                SourceStartPosition = sourcePosition,
-                SourceEndPosition = processor.Line.End,
+                Span = new SourceSpan(sourcePosition, processor.Line.End),
             });
             return BlockState.Continue;
         }
@@ -62,7 +61,7 @@ namespace Markdig.Parsers
             var c = processor.CurrentChar;
             if (c != quote.QuoteChar)
             {
-                block.SourceEndPosition = processor.Start - 1;
+                block.Span.End = processor.Start - 1;
                 return processor.IsBlankLine ? BlockState.BreakDiscard : BlockState.None;
             }
 
@@ -72,7 +71,7 @@ namespace Markdig.Parsers
                 processor.NextChar(); // Skip following space
             }
 
-            block.SourceEndPosition = processor.Line.End;
+            block.Span.End = processor.Line.End;
             return BlockState.Continue;
         }
 
@@ -81,7 +80,7 @@ namespace Markdig.Parsers
             var quoteBlock = block as QuoteBlock;
             if (quoteBlock?.LastChild != null)
             {
-                quoteBlock.SourceEndPosition = quoteBlock.LastChild.SourceEndPosition;
+                quoteBlock.Span.End = quoteBlock.LastChild.Span.End;
             }
             return true;
         }

src/Markdig/Parsers/ThematicBreakParser.cs

@@ -88,8 +88,7 @@ namespace Markdig.Parsers
             processor.NewBlocks.Push(new ThematicBreakBlock(this)
             {
                 Column = processor.Column,
-                SourceStartPosition = startPosition,
-                SourceEndPosition = line.End
+                Span = new SourceSpan(startPosition, line.End)
             });
             return BlockState.BreakDiscard;
         }

src/Markdig/Properties/AssemblyInfo.cs

@@ -25,6 +25,6 @@ namespace Markdig
 {
     public static partial class Markdown
     {
-        public const string Version = "0.5.0";
+        public const string Version = "0.5.2";
     }
 }

src/Markdig/Syntax/ContainerBlock.cs

@@ -69,9 +69,9 @@ namespace Markdig.Syntax
             children[Count++] = item;
             item.Parent = this;
 
-            if (item.SourceEndPosition > SourceEndPosition)
+            if (item.Span.End > Span.End)
             {
-                SourceEndPosition = item.SourceEndPosition;
+                Span.End = item.Span.End;
             }
         }
 

src/Markdig/Syntax/Inlines/LinkDelimiterInline.cs

@@ -25,6 +25,11 @@ namespace Markdig.Syntax.Inlines
         /// </summary>
         public string Label { get; set; }
 
+        /// <summary>
+        /// The label span
+        /// </summary>
+        public SourceSpan LabelSpan;
+
         public override string ToLiteral()
         {
             return IsImage ? "![" : "[";

src/Markdig/Syntax/Inlines/LinkInline.cs

@@ -54,9 +54,34 @@ namespace Markdig.Syntax.Inlines
         /// </summary>
         public string Title { get; set; }
 
+        /// <summary>
+        /// Gets or sets the label.
+        /// </summary>
+        public string Label { get; set; }
+
         /// <summary>
         /// Gets or sets a value indicating whether this instance is an image link.
         /// </summary>
         public bool IsImage { get; set; }
+
+        /// <summary>
+        /// Gets or sets the reference this link is attached to. May be null.
+        /// </summary>
+        public LinkReferenceDefinition Reference { get; set; }
+
+        /// <summary>
+        /// The URL source span.
+        /// </summary>
+        public SourceSpan? UrlSpan;
+
+        /// <summary>
+        /// The title source span.
+        /// </summary>
+        public SourceSpan? TitleSpan;
+
+        /// <summary>
+        /// The label span
+        /// </summary>
+        public SourceSpan? LabelSpan;
     }
 }

src/Markdig/Syntax/LinkReferenceDefinitionExtensions.cs

@@ -11,56 +11,46 @@ namespace Markdig.Syntax
     /// </summary>
     public static class LinkReferenceDefinitionExtensions
     {
-        private static readonly object DocumentKey = typeof(LinkReferenceDefinition);
+        private static readonly object DocumentKey = typeof(LinkReferenceDefinitionGroup);
 
         public static bool ContainsLinkReferenceDefinition(this MarkdownDocument document, string label)
         {
             if (label == null) throw new ArgumentNullException(nameof(label));
-            var references = document.GetData(DocumentKey) as Dictionary<string, LinkReferenceDefinition>;
+            var references = document.GetData(DocumentKey) as LinkReferenceDefinitionGroup;
             if (references == null)
             {
                 return false;
             }
-            return references.ContainsKey(label);
+            return references.Links.ContainsKey(label);
         }
 
         public static void SetLinkReferenceDefinition(this MarkdownDocument document, string label, LinkReferenceDefinition linkReferenceDefinition)
         {
             if (label == null) throw new ArgumentNullException(nameof(label));
             var references = document.GetLinkReferenceDefinitions();
-            references[label] = linkReferenceDefinition;
-        }
-
-        public static bool RemoveLinkReferenceDefinition(this MarkdownDocument document, string label)
-        {
-            if (label == null) throw new ArgumentNullException(nameof(label));
-            var references = document.GetData(DocumentKey) as Dictionary<string, LinkReferenceDefinition>;
-            if (references == null)
-            {
-                return false;
-            }
-            return references.Remove(label);
+            references.Set(label, linkReferenceDefinition);
         }
 
         public static bool TryGetLinkReferenceDefinition(this MarkdownDocument document, string label, out LinkReferenceDefinition linkReferenceDefinition)
         {
             if (label == null) throw new ArgumentNullException(nameof(label));
             linkReferenceDefinition = null;
-            var references = document.GetData(DocumentKey) as Dictionary<string, LinkReferenceDefinition>;
+            var references = document.GetData(DocumentKey) as LinkReferenceDefinitionGroup;
             if (references == null)
             {
                 return false;
             }
-            return references.TryGetValue(label, out linkReferenceDefinition);
+            return references.TryGet(label, out linkReferenceDefinition);
         }
 
-        public static Dictionary<string, LinkReferenceDefinition> GetLinkReferenceDefinitions(this MarkdownDocument document)
+        public static LinkReferenceDefinitionGroup GetLinkReferenceDefinitions(this MarkdownDocument document)
         {
-            var references = document.GetData(DocumentKey) as Dictionary<string, LinkReferenceDefinition>;
+            var references = document.GetData(DocumentKey) as LinkReferenceDefinitionGroup;
             if (references == null)
             {
-                references = new Dictionary<string, LinkReferenceDefinition>(StringComparer.OrdinalIgnoreCase);
+                references = new LinkReferenceDefinitionGroup();
                 document.SetData(DocumentKey, references);
+                document.Add(references);
             }
             return references;
         }

src/Markdig/Syntax/LinkReferenceDefinitionGroup.cs

@@ -0,0 +1,44 @@
+// Copyright (c) Alexandre Mutel. All rights reserved.
+// This file is licensed under the BSD-Clause 2 license. 
+// See the license.txt file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+
+namespace Markdig.Syntax
+{
+    /// <summary>
+    /// Contains all the <see cref="LinkReferenceDefinition"/> found in a document.
+    /// </summary>
+    /// <seealso cref="Markdig.Syntax.ContainerBlock" />
+    public class LinkReferenceDefinitionGroup : ContainerBlock
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="LinkReferenceDefinitionGroup"/> class.
+        /// </summary>
+        public LinkReferenceDefinitionGroup() : base(null)
+        {
+            Links = new Dictionary<string, LinkReferenceDefinition>(StringComparer.OrdinalIgnoreCase);
+        }
+
+        /// <summary>
+        /// Gets an association between a label and the corresponding <see cref="LinkReferenceDefinition"/>
+        /// </summary>
+        public Dictionary<string, LinkReferenceDefinition> Links { get; }
+
+        public void Set(string label, LinkReferenceDefinition link)
+        {
+            if (link == null) throw new ArgumentNullException(nameof(link));
+            Links[label] = link;
+            if (!Contains(link))
+            {
+                Add(link);
+            }
+        }
+
+        public bool TryGet(string label, out LinkReferenceDefinition link)
+        {
+            return Links.TryGetValue(label, out link);
+        }
+    }
+}

src/Markdig/Syntax/MarkdownObject.cs

@@ -10,6 +10,11 @@ namespace Markdig.Syntax
     /// </summary>
     public abstract class MarkdownObject : IMarkdownObject
     {
+        protected MarkdownObject()
+        {
+            Span = SourceSpan.Empty;
+        }
+
         /// <summary>
         /// The attached datas. Use internally a simple array instead of a Dictionary{Object,Object}
         /// as we expect less than 5~10 entries, usually typically 1 (HtmlAttributes)
@@ -29,21 +34,18 @@ namespace Markdig.Syntax
         public int Line { get; set; }
 
         /// <summary>
-        /// Gets or sets the starting character position from the original text source. 
-        /// Note that for inline elements, this is only valid if <see cref="MarkdownExtensions.UsePreciseSourceLocation"/> is setup on the pipeline.
+        /// The source span
         /// </summary>
-        public int SourceStartPosition { get; set; }
+        public SourceSpan Span;
 
         /// <summary>
-        /// Gets or sets the ending character position from the original text source.
-        /// Note that for inline elements, this is only valid if <see cref="MarkdownExtensions.UsePreciseSourceLocation"/> is setup on the pipeline.
+        /// Gets a string of the location in the text.
         /// </summary>
-        public int SourceEndPosition { get; set; }
-
-        /// <summary>
-        /// Gets the character length of this element within the original source code.
-        /// </summary>
-        public int SourceLength => SourceEndPosition - SourceStartPosition + 1;
+        /// <returns></returns>
+        public string ToPositionText()
+        {
+            return $"${Line}, {Column}, {Span.Start}-{Span.End}";
+        }
 
         /// <summary>
         /// Stores a key/value pair for this instance.

src/Markdig/Syntax/SourceSpan.cs

@@ -0,0 +1,80 @@
+// Copyright (c) Alexandre Mutel. All rights reserved.
+// This file is licensed under the BSD-Clause 2 license. 
+// See the license.txt file in the project root for more information.
+
+using System;
+
+namespace Markdig.Syntax
+{
+    /// <summary>
+    /// A span of text.
+    /// </summary>
+    public struct SourceSpan : IEquatable<SourceSpan>
+    {
+        public static readonly SourceSpan Empty = new SourceSpan(0, -1);
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="SourceSpan"/> struct.
+        /// </summary>
+        /// <param name="start">The start.</param>
+        /// <param name="end">The end.</param>
+        public SourceSpan(int start, int end)
+        {
+            Start = start;
+            End = end;
+        }
+
+        /// <summary>
+        /// Gets or sets the starting character position from the original text source. 
+        /// Note that for inline elements, this is only valid if <see cref="MarkdownExtensions.UsePreciseSourceLocation"/> is setup on the pipeline.
+        /// </summary>
+        public int Start { get; set; }
+
+        /// <summary>
+        /// Gets or sets the ending character position from the original text source.
+        /// Note that for inline elements, this is only valid if <see cref="MarkdownExtensions.UsePreciseSourceLocation"/> is setup on the pipeline.
+        /// </summary>
+        public int End { get; set; }
+
+        /// <summary>
+        /// Gets the character length of this element within the original source code.
+        /// </summary>
+        public int Length => End - Start + 1;
+
+        public bool IsEmpty => Start > End;
+
+        public bool Equals(SourceSpan other)
+        {
+            return Start == other.Start && End == other.End;
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (ReferenceEquals(null, obj)) return false;
+            return obj is SourceSpan && Equals((SourceSpan) obj);
+        }
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                return (Start*397) ^ End;
+            }
+        }
+
+        public static bool operator ==(SourceSpan left, SourceSpan right)
+        {
+            return left.Equals(right);
+        }
+
+        public static bool operator !=(SourceSpan left, SourceSpan right)
+        {
+            return !left.Equals(right);
+        }
+
+        public override string ToString()
+        {
+            return $"{Start}-{End}";
+        }
+    }
+}

src/Markdig/project.json

@@ -1,6 +1,6 @@
 {
   "title": "Markdig",
-  "version": "0.5.0",
+  "version": "0.5.2",
   "authors": [ "Alexandre Mutel" ],
   "description": "A fast, powerfull, CommonMark compliant, extensible Markdown processor for .NET",
   "copyright": "Alexandre Mutel",
@@ -11,7 +11,7 @@
     "projectUrl": "https://github.com/lunet-io/markdig",
     "iconUrl": "https://raw.githubusercontent.com/lunet-io/markdig/master/img/markdig.png",
     "requireLicenseAcceptance": false,
-    "releaseNotes": "Add support for precise source location pipelineBuilder.UsePreciseSourceLocation. Breaking change: Markdown.ToHtml() accept now only a string instead of a TextReader as this improve the overall performance.",
+    "releaseNotes": "> 0.5.2:\nAdd better support for precise source location for link parts (label, url...)\n> 0.5.1:\nAdd support for task lists.\nAdd support for precise source location pipelineBuilder.UsePreciseSourceLocation.\nBreaking change: Markdown.ToHtml() accept now only a string instead of a TextReader as this improve the overall performance.",
     "tags": [ "Markdown CommonMark md html md2html" ]
   },
   "configurations": {